Anatomy and Histology of the Breast Flashcards
The breast is a subcutaneous organ. What does this tell us about its position?
- It is anterior to the muscles of the body wall
- subcutaneous indicates it is an organ within the skin
How is the breast divided?
- 15-25 lobes
- each contain lobules (compound tubulo-acinar glands)
- these drain to the nipple via a series of ducts
- Septa between lobes is made up of dense CT
- Adipose tissue surrounds the dense connective tissue
What name is given to the duct belonging to each lobe of the breast?
Lactiferous duct
=> these converge at the nipple
What does the word “compound” indicate when describing breast lobules as “compound tubulo-acinar glands”
Indicates that the duct system is branching
An expansion occurs in the lactiferous duct as it reaches the nipple. What is this known as?
Lactiferous sinus
What other name is given to the dense aggregations of connective tissue causing septa between the lobes of the breast
Suspensory ligaments
- these also act to suspend the breast from either the clavicles or the deep fascia
- more of these ligaments are present in the upper portion of the breast for this purpose
What is the basic functional secretory unit in the breast?
Terminal Duct Lobular Unit (TDLU)
Explain the flow of secretions from the Terminal Duct Lobular Unit (TDLU) to the nipple?
Terminal ductules
- > intralobular collecting duct
- > lactiferous duct for that lobe
This leads to the nipple, passing through the lactiferous sinus
Describe the difference in the type of connective tissue found inside and outside the lobules of the breast?
Dense connective tissue surrounding the lobule (OUTSIDE)
Looser connective surrounding the acini (INSIDE)
Why is loose connective tissue found inside the lobules of the breast?
It allows rapid expansion in pregnancy
The acini of the lobules are lined by what cells?
- secretory epithelial cells (vary from cuboidal to columnar)
- these are then surrounded by surrounded by myoepithelial cells (contractile)
Describe the epithelial lining of larger ducts such as the lactiferous ducts
- varies from thin stratified squamous to stratified cuboidal
- Myoepithelial cells are still present
What is the red staining that is present in the lactiferous ducts on histology?
Coagulated proteins being secreted
Mammary glands are often seen as a modification of which other existing gland?
Sweat gland
- secretory
- found in the skin (s/c organ)
Describe the structure of the nipple
- wrinkled surface
=> thin, highly pigmented keratinized stratified squamous epithelium (EPIDERMIS) - core of dense irregular connective tissue (DERMIS) with bundles of smooth muscle (NOT usually found in skin)
- Many sebaceous glands open directly onto the surface of the nipple (different to normal skin where this would occur via a hair follicle)
Describe how the composition of the breast even changes in pregnancy
FOLLICULAR phase
- cells are shorter and closer together
- lumen of duct systems are difficult to identify
LUTEAL phase
- epithelial cells increase in height
- lumen of the ducts = enlarged and more obvious
- small amounts of secretions appear in the ducts.
Describe the dramatic changes that take place during each trimester of pregnancy?
1st Trimester:
- elongation and branching of smaller ducts
- proliferation of epithelial and the myoepithelial cells
2nd Trimester:
- Glandular tissue develops with differentiation of secretory alveoli (acini)
- Plasma cells and lymphocytes infiltrate nearby connective tissue
3rd Trimester:
- Secretory alveoli mature
- Development of extensive rER (for protein production to go into milk)
What two types of tissue in the breast tend to reduce in amount when a woman becomes pregnant?
Connective and adipose tissue
Describe how a lactating breast can be identified on histology
- secretory alveoli have matured and appear as swollen regions
- only a few adipose cells remain in the septa
- epithelial elements appear more proliferative
- Plasma cells can be identified (large, pink to due rER proteins, clock face nuclei)
What is the purpose of plasma cells in the breast tissue?
IgA production to be secreted into colostrum and eventually breast milk
Describe the composition of human milk
88% water
1.5% protein (lactalbumin and casein)
7% carbohydrate (mainly lactose)
3.5% lipid
Small quantities of: ions, vitamins and IgA
Describe how Lipid droplets are secreted into breast milk?
Apocrine secretion
- Like exocytosis BUT with a membrane and small amount of cytoplasm encompassing the secreted droplet
Describe how proteins made in the rER are secreted into the breast milk?
Merocrine secretion (exocytosis)
- Secreted via vesicles (v)
- These merge with the apical membrane to release only their contents into the duct system
What other form of secretion is possible from the glands in the breast tissue?
Holocrine Secretion
- involves death of entire cell
- cell fills with sebum droplets
- cell bursts open and expels contents
Describe the changes in the breast structure that occur after the menopause?
- secretory cells of TDLU’s degenerate
- leaves only ducts behind
- connective tissue = fewer fibroblasts, collagen and elastic
